For many women, premenstrual syndrome, or PMS, is a familiar preamble to their monthly cycle. But a new review of the data suggests that mood changes aren’t as closely tied to menses as many have assumed.

A team led by Dr. Sarah Romans of the University of Otago in New Zealand reviewed 47 studies that followed women’s moods across the menstrual cycle. Only 15% of the studies found that women tended to have “classic” PMS: moods that worsened as the menstrual period approached and lifted when menstruation occurred. An additional 38% found PMS that lasted into menstruation or another cycle phase.

However, a further 38% of the studies found no association between mood and any particular phase of the cycle. And 9% found that the worst moods actually occurred outside of the premenstrual phase. That means that little more than half of the studies (53%) found any link between menstruation and bad mood, and 85% didn’t find classic PMS.

“The major finding of this review was that clear evidence for a specific premenstrual-phase-related mood occurring in the general population is lacking,” the authors conclude.

Nonetheless, the idea of moodiness occurring cyclically in women has a long-standing history. The authors cite a “long-established tendency to label women’s behavior as overly emotional and to attribute this to female reproductive function.”

So is the concept of PMS just a remnant of sexist ideas about women’s changing moods from a time when most physicians were male? The new study unfortunately isn’t designed to provide an answer. For one thing, because they wanted to look at healthy women, the authors excluded data on women seeking help for premenstrual dysphoric disorder (PMDD), a syndrome they do not dispute, in which 1% to 9% of women experience extreme mood problems related to the menstrual cycle.

Second, given the wide range of factors that affect mood, it’s difficult to distinguish the effects of changing hormone levels. Some of the studies, for example, found mood changes related to the day of the week (in one, Fridays were happy, Tuesdays not so much), and others found, not surprisingly, that stressful events had a greater impact on mood than the cycle did.

“It makes sense to me that they would find little to no effect of PMS on mood when looking at the big picture,” says Kathryn Clancy, an assistant professor of anthropology at the University of Illinois who studies reproductive behavior but was not associated with the research. “Overall, PMS is not only physiologically dependent but culturally dependent. There are studies that show women have different PMS symptoms depending on their country of origin.”

In fact, she says, citing a classic feminist text that describes menstruation, some women even use the idea to subvert culturally restricting concepts about femininity and feminine behavior. “It’s almost as if, given cultural expectations that they will behave badly, they decide to go along with it in order to behave in the ways normally inaccessible to them, [like] being bossy, irritable [or] bold,” she says.

Still, this doesn’t mean sex hormones have no effect. The hormone that dominates the second half of the cycle, progesterone, has a powerful influence. Some studies show that progesterone can reduce anxiety, and in animal studies, when levels drop — as they do around menstruation — symptoms of depression can occur.

Since many women in the data showed cycle-related mood changes, the most likely explanation is that varying hormone levels have different effects on mood in different women — a sensible, if not very satisfying, conclusion.

And as for the tradition of portraying women as victims of their changing hormones, it’s possible that men experience the same fluctuations in testosterone, with similar ups and downs in mood and emotional stability. It’s just that it may be easier to attribute the mood swings in women to reproductive hormones because tracking the menstrual cycle provides a noninvasive window into their fluctuations.

So while the new review suggests that most women don’t have a predictable pattern of low moods preceding their periods, it doesn’t exonerate reproductive hormones from having any role in how people feel. And new technology may soon provide far better data for both men and women to find any correlations that exist in their own lives: smart-phone apps that help track changing moods, for example, may soon give researchers deeper insight into individual patterns that may or may not be linked to sex hormones.